Aircraft jet engines include one or a plurality of compressor stages, a combustion chamber, and one or a plurality of turbine stages. The hot exhaust gases emanating from the combustion chamber release part of their thermal and mechanical energy in the turbine stages, said energy being utilized for driving the compressor stages. The majority of jet engines for commercial aircraft today have a so-called turbofan which is disposed upstream of the compressor stages and typically has a diameter which is significantly larger than that of the compressor stages. The turbofan is likewise driven by the turbine stages and allows a significant part of the total air volume which perfuses the jet engine to flow past the compressor stages, the combustion chamber, and the turbine stages, as a so-called bypass flow. By way of such a bypass flow the efficiency of an engine may be significantly increased, moreover allowing for improved noise insulation of the engine.
Contamination of an aircraft jet engine may lead to reduced efficiency, resulting in increased fuel consumption and thus to increased environmental burden. Contamination may be caused, for example, by insects, dust, salt spray, or other types of environmental contamination. Parts of the engine may be contaminated by combustion residues from the combustion chamber. These types of contamination form a layer on those parts of an aircraft engine that are perfused by air, compromising the surface finish. The thermodynamic efficiency of the engine is thus compromised. Here, particular mention should be made of the blades in the compressor stages, the contamination of which blades has a significant effect on the efficiency of the entire engine.
In order for contamination to be removed it is known for an engine to be cleaned using a cleaning fluid, typically hot water. An assembly in which a plurality of cleaning nozzles are disposed upstream of the turbofan, or of the compressor stages, respectively, is known from WO 2005/120953. The cleaning fluid is then sprayed into the engine. Here, the engine may be rotated in the so-called dry cranking mode, that is to say that the blades of the engine are rotated without kerosene being combusted in the combustion chamber. Contamination is to be washed off the surfaces of the engine components by way of the cleaning fluid which is introduced into the engine.
As an alternative to the use of water as a cleaning medium, the use of carbon dust is known. Here, the carbon dust, like the water, is introduced into the engine through nozzles, removing contamination from surfaces by virtue of abrasive effects. However, the surfaces of the engine components are also affected by the carbon dust, which is why a cleaning medium such as carbon dust is not suitable for regular cleaning of aircraft engines. Moreover, when cleaning using carbon dust, undesirable remnants of the cleaning material remain in the engine. WO 2009/132847 A1 discloses a device and a method for cleaning jet engines, using solid carbon dioxide as a cleaning medium.